The invention is based on a priority application EP 02 360 301.2 which is hereby incorporated by reference.
The invention relates to a method to provide an operator selection service for subscribers of a communications network and to a communications network, and a call server.
Traditionally, telephone subscribers of one country or one region of a country were all served by only one national or regional carrier network, further called incumbent carrier.
The terminals of a public telephone network are physically connected to different local exchanges of said incumbent carrier depending on their location. Call connections traditionally are established directly by the local exchange, if both subscribers belong to the same region, i.e. if both subscribers are connected to the same local exchange. In this case a so-called local call is carried out without involving any other exchanges.
Differently, for long distance calls, a connection has to be established over a chain of exchanges, wherein said exchanges are often grouped in hierarchical order. For a long distance call establishment, signalling information has to exchanged between all affected exchanges. In modern telephone networks according to well known Integrated Services Digital Networks (ISDN) standards, said signalling information is exchanged by means of specific protocols over a separate signalling network, forming a so-called signalling system number seven (SS7).
In recent years, national authorities of a plurality of countries decided to open the telecommunication market to competitors. As it is extremely expensive to build up separate networks providing physical access to customer terminals, a solution was chosen, wherein the customer terminals may remain physically connected to local exchanges of the incumbent carrier, but may select different carriers for further call service. This selection may be carried out either on call-by-call basis, wherein for each call the user may select an appropriate carrier by dialling a prefix number, or on pre-selection basis, where each call of a customer is forwarded to the selected carrier by said customer. With this solutions, customers can select competitive carriers different from the incumbent carrier without changing any physical access.
In a lot of countries, carrier selection is already possible for long distance calls, i.e. for calls, that cannot be handled by the local exchange alone. The incumbent carrier, receiving a call request at a local exchange, need to distinguish between calls, that are to be forwarded to further exchanges of his own network and that are to be forwarded to a so-called competitors local exchange.
Legislation in a lot of countries, e.g. in Germany and in France will force to further open the incumbent networks even for local calls. As a variant or a development of a solution used for carrier selection for long distance calls, wherein local exchanges of competitors are connected to local exchanges of incumbent carriers, a solution assumed as prior art solution for enabling local call selection service is shown in FIG. 1.
FIG. 1 shows a connection oriented communications network CN, i.e. a telephone network, comprising by way of example one local exchange ILEX of an incumbent carrier, further called incumbent local exchange ILEX. Further, the communications network CN comprises a local exchange of a competitor, in the following called competitive local exchange CLEX. By way of example, a first port X1 (outgoing port) of the incumbent local exchange ILEX is connected to one port of the competitive local exchange CLEX by an outgoing line OL, and a second port X2 (ingoing port) of the incumbent local exchange ILEX is connected to one further port of the competitive local exchange CLEX by an ingoing line IL. The ingoing and the outgoing line IL and OL each comprise a bundle of a certain number of communication trunks, e.g. one so-called PCM 30 system defined within the framework of ISDN and comprising 30 communication trunks. Further, a number of n terminals T1, T2, . . . , Tn is connected to the incumbent local exchange ILEX.
Traditionally, in case of local calls, all of said terminals T1, T2, . . . , Tn, e.g. calls between terminal T1 and terminal T2, were served by the incumbent local exchange ILEX and were solely served by said exchange. Here, by way of example, the subscribers have the opportunity to choose between the incumbent operator and a competitive operator, each having installed an own local exchange ILEX and CLEX respectively. If a subscriber e.g. of the first terminal, selects the incumbent operator, he is still served as traditionally. If he selects the competitive operator, the corresponding call needs to be forwarded from the incumbent local exchange ILEX to the competitive local exchange CLEX. Therefore, the incumbent local exchange ILEX, after detecting, that said call has to be transferred to a competitor and identifying the specific competitor, if more that one competitor is existing, sends corresponding call information to the identified competitive local exchange CLEX, normally comprising the calling number and the called number, over the signalling network SS7 to said competitive local exchange CLEX. Here, it is assumed, that the communications network CN represents a so-called integrated services digital network (ISDN), wherein signalling information between the network nodes, i.e. the exchanges ILEX and CLEX in the example of FIG. 1, is transmitted over a separate signalling network SS7, called signalling system (number) 7.
The competitive local exchange CLEX looks up, what service has to be carried out, e.g. to resolve the called number for identifying the physical address of the called subscriber, e.g. the calling number of the terminal T2, if said number represents a number of a so-called private virtual network. The competitive local exchange CLEX then sends back, over the signalling network SS7 a connection request to the incumbent local exchange ILEX to connect the corresponding terminals T1 and T2 to the ingoing line OL1 and to the outgoing line IL respectively. Further, charging the calling subscriber and/or the called subscriber is carried out by the competitive local exchange CLEX.
The provision of a separate local exchange per incumbent exchange area is expensive. Therefore, the above described solution will not be commercial profitable within small local area networks, i.e. for local exchanges with a fairly low number of connected terminals. Thus, local competitors will concentrate on cities of a greater size.